AstraZeneca and Daiichi Sankyo’s Breast Cancer Drug Hits Primary Endpoint

AstraZeneca logo on three outdoor flags

Roland Magnusson /

AstraZeneca and Daiichi Sankyo announced that their trastuzumab deruxtecan (DS-8201) hit its primary endpoint in HER2-positive, unresectable and/or metastatic breast cancer that had previously been treated with trastuzumab emtansine.

The Phase II DESTINY-Breast01 clinical trial is an open-label, global, multicenter, two-part trial looking at the safety and efficacy of trastuzumab deruxtecan in patients with HER2-positive unresectable and/or metastatic breast cancer who had received previous treatment with Genentech’s trastuzumab emtansine (Kadcycla). The primary endpoint was objective response rate (ORR). Secondary objectives included duration of response, disease control rate, clinical benefit rate, progression-free survival and overall survival.

In March, the two companies signed a deal to develop that drug, with AstraZeneca paying up to $6.9 billion on it. The drug targets the HER2 protein, which triggers uncontrolled cell growth in approximately 20% of cancers. Roche/Genentech’s Herceptin (trastuzumab) is part of Kadcycla. Kadcycla is an antibody conjugate (ABC), or a chemotherapeutic molecularly linked to an antibody that targets cancer cells.

Alistair Campbell, an analyst with Liberum, wrote in a note to clients, “While positive data will have been expected given the Phase I data, this is good news for (AstraZeneca) as it adds validation of a major transaction that initially disappointed the market.”

Specifics of the data were not released. The two companies plan to present it at a future medical meeting.

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HER2-positive breast cancer accounts for about 20% of breast cancers. They typically advance to the point where no currently approved HER2-targeting drugs continue to work.

Trastuzumab deruxtecan has received the U.S. Food and Drug Administration (FDA)’s Breakthrough Therapy Designation and Fast Track Designation.

On April 29, the two companies announced that data from the Phase I trial of the drug had been published in two articles in The Lancet Oncology. The first manuscript described data for 115 patients who’d received at least one dose of the drug, of which 111 were evaluated for confirmed response. Patients in that part of the trial had a median of seven previous treatments, including trastuzumab and trastuzumab emtansine, and in 86% of cases, pertuzumab. The confirmed ORR was 59.5% and a disease control rate (DCR) of 93.7%. Median duration of response (DoR) was 20.7 months and median progression-free survival (PFS) was 22.1 months.

The second paper described safety results for 115 patients with HER2-positive MBC who received at least one dose of trastuzumab deruxtecan in part one or part two of the trial. The most common side effects were nausea, decreased appetite, vomiting, alopecia, fatigue, anemia, diarrhea and constipation.

The two companies say that the results of the Phase II trial are consistent with those published in the Phase I trial.

AstraZeneca and Daiichi Sankyo indicated they plan to submit the drug to the FDA in the second half of this year. Trastuzumab deruxtecan is also an ADC. The drug is involved in a number of clinical trials, five which are near final stages.

“These results confirm our commitment to pursue accelerated regulatory pathways in HER2-positive metastatic breast cancer with trastuzumab deruxtecan,” stated Antoine Yver, executive vice president and Global Head, Oncology Research and Development, for Daiichi Sankyo. “We are more dedicated than ever to our comprehensive and ambitious development strategy evaluating the potential across a spectrum of HER2-expressing cancers including breast, gastric, lung and colorectal.”

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